An amplifier is designed to provide constant gain to an input signal to generate an amplified output signal. An amplifier is usually able to provide constant gain only over a limited operating range of input and output signals. If the magnitude of the input or output signal falls outside the operating range, the amplifier may exhibit gain compression and/or other non-linear characteristics.
One way to extend the operating range of the amplifier is to increase the gain when the signal falls outside the operating range. In transistor amplifier designs, the gain provided to a signal is often related to the amount of current used to bias the transistor or transistors in a gain stage of the amplifier. Typically, greater current consumption increases gain, while lower current consumption saves power.
It would be desirable to dynamically adjust the biasing of the transistors in the amplifier to extend the operating range of the amplifier when necessary, while conserving power during normal operation.